Mercury is the smallest planet in our solar system and the closest one to the sun. Named after the Roman messenger god, it whizzes around the sun at a distance of just 36 million miles, completing a full orbit in just 88 Earth days. Because of its proximity to the sun, Mercury is an extremely hot and inhospitable planet, with daytime temperatures reaching up to 800 degrees Fahrenheit and nighttime temperatures dropping to -290 degrees Fahrenheit. Despite its small size, Mercury is a fascinating planet with some interesting characteristics. For one, it has a very thin atmosphere, which is made up of mostly helium and hydrogen. Another interesting fact is that Mercury has a unique rotation pattern; it rotates on its axis exactly three times for every two orbits it makes around the sun. This means that one day on Mercury is actually longer than one year. Day Length: 58.6 Day || Diameter: 4,879 KM || Year Length: 87.97 Days